Relative Oxygen Concentration Research Articles

Mechanical Properties of V-O-N Coatings Synthesized by Cathodic Arc Evaporation.

The V-O-N coating set was produced at different relative oxygen concentrations of O2(x) = O2/(N2 +O2) using cathodic arc evaporation. The aim of the research was to determine the effect of oxygen on coating properties. The coatings' composition and structural properties (X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX)) and mechanical properties-hardness, adhesion, and wear resistance (nano-indenter, scratch tester, ball-on-disc tester)-were extensively investigated. EDX and XRD analyses indicate that in coatings formed with a relative oxygen concentration in the range of 20-30%, the oxygen concentration in the coating increases dramatically from approximately 16 at.%. to 63 at.%, and the nitrogen concentration drops from about 34 at.% up to 3 at.%. This may indicate greater activity of oxygen compared to nitrogen in forming compounds with vanadium. The occurrence of the V5O9 phase belonging to the Magnéli phases was observed. Microscopic observations indicate that the number of surface defects increases with the oxygen concentration in the coating. The opposite effect is characterized by mechanical properties-hardness, adhesion, and wear resistance decrease with increasing oxygen concentration in the coating.

Infrared study of the structure of silicon oxynitride films produced by plasma enhanced chemical vapor deposition

The structure of thin (∼300nm) SiOxNy (0.23≤x≤1.95, 0.01≤y≤0.32) films produced by plasma enhanced chemical vapor deposition is studied by infrared (IR) spectroscopy. The dependence of the shape of the main IR absorption band in the range of 700–1400 cm–1 upon film composition is analyzed. The IR spectra exhibit strong overlapping of the bands corresponding to absorption on Si–O and Si–N bonds. A problem of separating these components is solved. Analysis of their relative intensities provides an insight into the film structure. The films with high oxygen content are found to have a homogeneous structure similar to that of nonstoichiometric Si oxide that can be described by the random bonding model. Increase of relative Si concentration and simultaneous decrease of oxygen and nitrogen content changes the film structure to the two-phase one obeying the random mixture model. Such material may be represented as a uniform mixture of interconnecting silicon–oxygen tetrahedra (Si–OaSi4-a, a=0..4) and silicon–nitrogen pyramids (Si3N). Relative Si concentration in the Si oxynitride films and their deposition temperature are hypothesized to play a decisive role on their structure, which is supported by thermodynamic modeling.

The atomic oxygen resistant study of a transparent polyimide film containing phosphorus and fluorine

As ideal packaging materials for solar cells of low-Earth orbit (LEO) spacecraft, polyimide (PI) films have to withstand various harsh space environment. Here, we investigate the atomic oxygen (AO)-resistant property of a transparent PI film with side diphenylphosphine oxide and trifluoromethyl. After exposed under AO (1.3 × 1020 atoms·cm−2), most excellent properties of the PI film can be maintained except for partial loss of transmittance. Its erosion yield is 0.56 × 10−24 cm3·atom−1, only 18.7% as that of Kapton film at the same condition. To understand the damage mechanism, the surface and bulk performances of the AO exposed PI film were systematically investigated and compared with those of the prinstine PI film. The results indicate that the relative concentration of phosphorus and oxygen near to the AO exposed surface of the PI film increases, which means the formation of a phosphate passivation layer. The thickness of phosphate passivation layer is about 200 nm with the content of PO3− decreasing in vertical direction of itself, which can reduce the further erosion of the PI film by AO. Such PI films containing P and F are much more AO resistant and expected a candidate as packaging material for LEO spacecraft.

Comparative Study of Atmosphere Effect on Wood Torrefaction

Climate change, biomass utilization, and bioenergy recovery are among the biggest current global concerns. Wood is considered an environmentally benign material. Nevertheless, it must be processed for desired applications. Upon thermal treatment ranging from 180 °C to 280 °C, under low oxygen concentrations, wood becomes a material with improved dimensional stability, resistance to fungal attacks, grindability, hydrophobicity, and storage stability. Several strategies for wood treatment have been investigated over the course of the past decades, including the use of steam, nitrogen, smoke, vacuum, water, and hot oil. The goal of this work is to investigate the influence of pressure and atmosphere on the torrefaction of poplar. Through a systematic analysis of poplar wood samples treated under reduced pressures and different atmospheres, while keeping the same heating profile, it was possible to establish that changes observed for mass loss, color change, wood composition (via TGA/DTG analysis), functional groups (via FTIR), elemental analysis, and X-ray diffractograms relate directly to known reaction pathways occurring during torrefaction. Changes observed under reduced pressures have been associated with the relative concentration of oxygen in the reaction atmosphere and to the reduced diffusion times experienced by reactive by-products during the treatment. Conversely, extended diffusion times resulted in more significant changes for reactions carried out under N2, water vapor, and air.

Polycyclic aromatic hydrocarbons (PAHs) and soot formations under different gasifying agents: Detailed chemical kinetic analysis of a two-stage entrained flow coal gasifier

The injection of CO2 with coal into coal gasifier is a promising approach to achieve CO2 recirculation. Predicting the formation and evolution of polycyclic aromatic hydrocarbons (PAHs) and soot during coal gasification is particularly important as their presence poses challenges to the gasifier operation and environment. However, the effect of CO2 injection on their formation must be elucidated in more detail to optimize the gasifier design. This work investigates PAHs and soot formations in gas-phase reactions under different gasifying agents (Air, O2/CO2, O2/H2O) in a two-stage entrained flow coal gasifier using a detailed chemical kinetic model (DCKM). Under the O2/CO2– and O2/H2O-blown conditions, aromatics reforming was progressed whereas the yields of tar and soot were effectively suppressed. The benzene was observed as the most abundant PAHs species, followed by naphthalene and acenaphthalene. Regarding the relative oxygen concentration, the conversion behavior of aromatics was significantly influenced in the O2/CO2-blown condition, while the somewhat effect was found in the O2/H2O-blown condition. Tar yield peaked at 50% relative oxygen concentration in the O2/CO2-blown condition. The present finding may have practical significance in the O2/CO2-blown gasifier to facilitate CO2 recirculation for the oxy-fuel IGCC system.

Life history in primate teeth is revealed by changes in major and minor element concentrations measured via field-emission SEM-EDS analysis.

Overcoming the non-specificity of histological accentuated growth lines in hard tissues is an ongoing challenge. Identifying season at death and reproductive events has profound implications for evolutionary, ecological and conservation studies. Dental cementum is a mineralized tissue with yearly periodicity that continues deposition from tooth formation until death, maintaining a record spanning almost the entire life of an individual. Recent work has successfully employed elemental analysis of calcified incremental tissues to detect changes in extrinsic conditions such as diet and climate and to identify two important life-history milestones: weaning and sexual maturity. Here, we employ field-emission scanning electron microscopy and energy-dispersive X-ray analysis to measure the relative concentrations of calcium, phosphorous, oxygen, magnesium and sodium in the cementum of 34 teeth from seven male and female rhesus macaques with known medical and life-history information. We find that changes in relative magnesium concentrations correspond with reproductive events in females and breastfeeding in infants. Additionally, we observe seasonal calcium patterns in 77.3% of the samples.

Influence of Relative Humidity and Oxygen Concentration on Corrosion Behaviour of Copper in H2S-Containing Liquid Petroleum Gas

In this paper, the influences of relative humidity (RH) and concentration of O2 on copper corrosion in H2S-containing LPG (liquid petroleum gas) were studied. The corrosion products obtained in different environments were also analysed by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). In H2S-containing LPG, RH has pronounced influence on the corrosion grade of copper. The variation in the critical point (CP) with the RH of LPG is a linear relationship. The presence of O2 in dry H2S has limited influence on the corrosion of copper. In the presence of different RHs, the CP always follows a negative exponential function with O2 concentration. The analysis of different corrosion products implies different corrosion behaviours and mechanisms, which are dependent on the presence or absence of water vapour. The corrosion mechanisms obtained in four different environments were also proposed.

Elemental composition of primary lamellar bone differs between parous and nulliparous rhesus macaque females.

Extracting life history information from mineralized hard tissues of extant and extinct species is an ongoing challenge in evolutionary and conservation studies. Primary lamellar bone is a mineralized tissue with multidien periodicity that begins deposition prenatally and continues until adulthood albeit with concurrent resorption, thus maintaining a record spanning several years of an individual's life. Here, we use field-emission scanning electron microscopy and energy-dispersive X-ray analysis to measure the relative concentrations of calcium, phosphorous, oxygen, magnesium and sodium in the femora of seven rhesus macaque with known medical and life-history information. We find that the concentration of these elements distinguishes parous from nulliparous females; that in females calcium and phosphorus are lower in bone formed during reproductive events; and that significant differences in relative magnesium concentration correlate with breastfeeding in infants.

Spectral sensitivity of the discoloration of Historical rag paper

This paper discusses the spectral sensitivity of the discoloration of historical rag paper simultaneously affected by Relative Humidity (RH) and Oxygen concentration [O2] in the ambient environment. Sacrificial samples were degraded using narrowband radiation sources centred at 450 nm, 525 nm, and 625 nm in combinations of RH and [O2] at two levels: 0% [O2] and 70% RH, 21% [O2] and 70% RH, 0% [O2] and 20% RH, and 21% [O2] and 20% RH. Diffuse reflectance was measured before and during the degradation experimental runs. Consistent qualitative results were obtained for the change in reflectance and the change in tristimulus total color change in CIELAB color space. In both cases, the increase of discoloration was modelled logarithmically over time. Among the three factors investigated in this research, wavelength of the radiation (Λ) was found to have the strongest effect. The radiation at 450 nm induced the most and fastest discoloration whereas the radiation at 625 nm induced the least and slowest discoloration. This spectral dependence was likely to be related to the photo energies at different wavelengths, but other factors were found to have played a role. Further analyses revealed that the main effects and the effects of the interactions between [O2] and Λ and between RH and Λ on the discoloration of historical rag paper were statistically significant. It suggests that managing the spectral power distribution of the radiation source can be crucial in the collection management.

Structure and Properties of ZrON Coatings Synthesized by Cathodic Arc Evaporation.

The transition metal oxynitrides are a coating material with decorative features due to their adjustable color and good mechanical properties. The purpose of the research was to study the effect of the relative oxygen concentration O2(x) = O2/(N2 + O2) in particular on adhesion, but also on the color, structural and mechanical properties of ZrON coatings synthesized by cathodic arc evaporation on HS6-5-2 steel substrates. The surface morphology, phase and chemical composition and mechanical properties were determined using scanning electron microscopy, X-ray diffraction, wavelength dispersive X-ray spectroscopy, nanoindentation and scratch test. It was found that color of the coatings changed from light yellow for ZrN first to gold and then to graphite for Zr-O phase with increase of oxygen concentration. X-ray diffraction patterns showed that the phase separation of ZrN and ZrO2 occurred for about 35 at.% of oxygen in the coating. Increase in oxygen concentration in the coatings led to decrease in crystallite size from about 20 nm for ZrN to about 5 nm for coatings with about 35 at.% of oxygen and about 25 at.% of nitrogen. An increase in hardness from about 26 GPa for ZrN to about 30 GPa for coating with small concentration of oxygen (about 9 at.%) and then decrease to about 15 GPa was observed. Adhesion of Zr-O-N coatings demonstrated strong dependence on oxygen concentration. Critical load for ZrN is about 80 N and decreases with oxygen concentration increase to about 30 N for ZrO2.

Determination of time constants of diffusion and electrochemical processes in Polymer Electrolyte Membrane Fuel Cells

This work presents an experimental analysis of the time constants associated to diffusion and electrochemical processes in a 50 cm2 Polymer Electrolyte Membrane (PEM) fuel cell. The experimental techniques and results include polarization curves and Electrochemical Impedance Spectroscopy (EIS) analysis of the fuel cell, where the time constants are determined from the analysis of the Distribution of Relaxation Times (DRT). EIS results are also used to determine the cell ohmic resistance, where High Frequency Resistance (HFR) values are calculated from the Nyquist plots. A wide range of operating conditions of the fuel cell are analysed, including back pressure (0.5 bar–1 bar), cell temperature (55 °C, 65 °C, 75 °C), reactant gases relative humidity (30%, 60%, 90%), cathode stoichiometry (λc 2.5–3.5), and oxygen concentration (air and pure oxygen). The effect of the operating conditions on the time constants are discussed, and Damköhler number is introduced and discussed.

(Invited) Ga2O3 Phase Control and Heterojunctions Using Plasma-Enhanced Atomic Layer Epitaxy

Ga2O3 has emerged as a promising material for next generation power electronics. While β-Ga2O3 (monoclinic) is the most stable and studied of six Ga2O3 polymorphs, the slightly less energetically favorable α-, ε-, and κ-Ga2O3 phases have unique characteristics that can be exploited such as larger bandgaps, alloying for dopant control, or polarization beneficial to the formation of two-dimensional electron gas (2DEG) channels. Specifically, α-Ga2O3 (rhombohedral, corundum) has the largest bandgap of ~5.3 eV and can be alloyed with α-Al2O3 (8.8 eV) and α-In2O3 (3.7 eV) for bandgap engineering. Both ε-Ga2O3 (hexagonal, P63mc) and κ-Ga2O3 (orthorhombic, Pna21 ) phases are polar, with a predicted spontaneous polarization strength up to 10 times larger than GaN and 3 times larger than AlN. Like the III-N system, polarization induced charges can lead to higher charge densities and mobilities in 2DEGs formed at heterojunctions, which would improve the viability of Ga2O3 electronic devices. Plasma-enhanced atomic layer deposition (PEALD) is a popular, conformal, energy-enhanced synthesis method for thin films due to its many advantages, including: deposition at reduced growth temperatures, access to metastable phases, improved crystallinity, and increased growth rates. In this work, we use PEALD to produce high-quality heteroepitaxial Ga2O3 and (AlxGa1-x)2O3 (AlGO) films and investigate materials properties such as phase selectivity, ternary solubility limits, and electrical and optical performance.All Ga2O3 films were deposited in a Veeco Fiji G2 reactor equipped with a load lock and turbo pump using trimethygallium, trimethylaluminum, and O2 plasma. Initial studies on c-plane sapphire substrates at 350°C and 8 mTorr show the phase could be altered from β to α by a varying the pure O2 flow during plasma pulse from 5-40 sccm [1]. Optical emission spectroscopy indicate that the changes in the relative concentration of atomic oxygen is crucial for phase selectivity while the high ion flux to the surface can contribute to the crystallinity at low Tg [2]. To grow ε(κ)-Ga2O3 on c-plane sapphire required going to a much higher temperature (500°C), pressure (100’s mTorr), and O2 flow (100sccm) [1]. Without modifications to the current ALD system, pure ε(κ)-Ga2O3 on sapphire was not achieved under any conditions. Using optimum growth conditions for the three phases on sapphire, films were deposited on GaN and diamond to determine the effect of substrate structure. Transmission electron microscopy was conducted to determine the specific phases (β, ε, and κ) present in each case, and showed the amount of each phase varied with PEALD parameters. While films on diamond resulted in mixed β/ε(κ) phases, pure ε(κ)-phase films were attained on GaN and the strain varied with pressure and Tg. Vertical breakdown measurements were taken for both β- and ε(κ)-Ga2O3/n+ GaN substrates. Breakdown fields varied between 3.8-7.0 MV/cm dependent on the phase and strained state of the Ga2O3 films. β-Ga2O3 films showed less variability in breakdown field from device to device than ε(κ)-Ga2O3 films, but neither showed a dependence on device size.While PEALD is beneficial for depositing thin films of metastable phases, practical devices often require much thicker barrier and active layers. For this reason, we investigated integrating PEALD metastable Ga2O3 films with traditional semiconductor deposition techniques, such as molecular beam epitaxy (MBE), capable of extending these layers beyond 100 nm in thickness. The same MBE conditions were used to deposit Ga2O3 films on GaN substrates with and without PEALD ε(κ)-Ga2O3 nucleation layers. Those deposited without the PEALD metastable nucleation layer resulted in stable β-phase films, while those with nucleation layers resulted in pure ε(κ)-phase films. This shows importance of PEALD for realizing practical device structures using metastable phases.Finally, to investigate heterojunctions for 2DEG formation, AlxGa1-xO films were developed. While the full stoichiometric range could be reached using a PEALD digital alloying method, crystallinity was lost above x = 0.2 for the β phase, x = 0.35 for the ε(κ) phase, and x=0.6 for the α phase. Initial device structures will be shown in order to establish the feasibility of these films in device applications.[1] Wheeler, et al. Chem. Mater. 2020, 32, 1140-1152[2] Boris, et al. JVST A 2019, 37(6), 060909 Figure 1

АКТУАЛЬНОСТЬ СОЗДАНИЯ ИСКУСТВЕННЫХ ДЫХАТЕЛЬНЫХ АТМОСФЕР В УСЛОВИЯХ ЗАГРЯЗНЕНИЯ АТМОСФЕРНОГО ВОЗДУХА

at present, the problem of air quality in large cities with a large number of cars and industrial enterprises is acute. Normative documents on the basis of which the ventilation system is designed regulate the cleaning of the outside air from dust. Purification from gaseous contaminants as well as suspended aerosols such documents do not regulate. According to the results of the study of air quality in Moscow over the past few years, an increased content of pollutants such as NO, CO, CO2, SO2 has been registered. Near busy highways during “rush hours” the vehicles locally “burn” oxygen in the air and emitted products of combustion even more reduce the relative concentration of oxygen in the air. Also, a large number of pollutants come from industrial and agricultural enterprises. The use of additional purification filters in ventilation systems, such as photocatalytic filter, adsorption filter can reduce the concentration of gaseous pollutants to an acceptable minimum, but they will not solve the problem of low oxygen content. Inhalation of air in excess of MPC for a long time may cause irreversible health effects. In this regard, the task of creating artificial respiratory atmospheres becomes relevant. The greatest relevance of air quality and sufficient oxygen content is for children's institutions, as well as special services, the work of which is associated with an increased concentration of attention. The problem of air pollution with aerosols and fine dust has become particularly relevant due to the significant increase in respiratory tract diseases and various allergies.

Simultaneous removal of NO and Hg0 in flue gas over Co-Ce oxide modified rod-like MnO2 catalyst: Promoting effect of Co doping on activity and SO2 resistance

The Co was firstly used as a dopant to improve the NO and Hg0 removal performance of CeO2 loaded rod-like MnO2 catalyst (Ce/MnO2) and its SO2 resistance. The results showed the doping process effectively improved the relative concentrations of chemisorbed oxygen as well as the contents of surface Ce4+ and Mn4+, enhanced the redox ability of catalyst, which was conducive to the simultaneous removal performance of NO and Hg0 in flue gas. The Co-Ce/MnO2 catalyst (the mole ratio of Co/Ce = 1.0) had optimal catalytic performance among all prepared catalysts in 160–280 °C, its NO and Hg0 removal efficiencies achieved 99.9% and 91.9% at 200 °C and 10,000 h−1, respectively. In addition, the Co-Ce/MnO2 performed stronger resistance to SO2 in comparison with Ce/MnO2, its catalytic activities decreased slightly when SO2 with a concentration of 500 ppm was added into the gas stream, and then recovered close to the initial value after eliminating of SO2. We considered the excellent SO2 tolerance performance of Co-Ce/MnO2 catalyst is assigned to the fact that the Co-modification restrained the sulfation of CeO2 and MnO2 to CeSO4 and MnSO4, alleviated the decreasing of chemisorbed oxygen, and hindered the chemisorption of SO2 on the catalyst. This work provided a promising prospect of Co-modification on Ce/MnO2 as SO2 resistant catalysts for simultaneous removal of NO and Hg0 from flue gas.

Rapid photolysis of H2S and the mechanism using high-frequency discharge electrodeless lamp

ABSTRACT In the present study, the H2S photolysis using the self-made high-frequency discharge electrodeless lamp (light distribution was 90% at 254 nm and 10% at 185 nm) was studied and simulated by MATLAB software. Firstly, the effects of the initial H2S concentration, irradiation time, oxygen content and relative humidity on H2S photolysis efficiency were experimentally investigated. The results indicated that the photolysis efficiency decreased from 100% to 90.13% with the increase in the initial concentration from 3 to 30 mg/m3, and the main product was H2SO4. With the relative humidity increased from 0% to 99%, H2S photolysis efficiency was obviously improved under different atmospheres (O2 > air > Ar), indicating the significant effect of relative humidity and oxygen concentration. The simulation results were consistent with the experimental results, indicating the feasibility of the simulation model. Moreover, based on the photoreactions, model simulation and equilibrium analysis of sulphur species, the photodegradation pathway of H2S was further inferred. H2S was oxidized to H2SO4 by O3 and other strong oxidizing radicals excited by 185 nm UV light.

Отношение организмов семейства Gammaridae к содержанию кислорода в придонном слое воды в Северном Каспии

The research of bottom invertebrates Gammaridae was carried out in 2013-2017 in the western part of the North Caspian. The purpose of the study was to determine the environmental tolerance of the organisms to oxygen. Oxygen deficit was caused by temperature and salinity stratification of water masses.Hypoxia was formed mainly in some areas of the shallow zone (up to 5 m) on the border of the Northern Caspian – Middle Caspian, as well as in areas with fine-grained sediments.Representatives of Gammaridae are characterized by high frequency of occur-rence.During the research period the number and biomass of the studied organisms widely varied. Gammarus Fabricius dominated by the total number, Dakerogammarus Stebbing – by the total biomass.The maximum frequency of occurrence was characteristic for Niphargoides similis (G. O. Sars).The limits of tolerance to oxygen of individual Gammaridae species living in the Northern Caspian sea have been presented.The minimum concentration of oxygen recorded for the entire period of research (1.29ml/l; 21%) is not critical for one species – Niphargoides similis (G. O. Sars). The low concentration (3 ml/l) does not inhibit the development of Niphargoides macrurus (Sars), Gammarus ischnus Stebbing, Gammarus pauxillus Grimm and Dikerogammarus haemobaphes (Eichwald). Other Gammaridae representatives living in the western part of the Northern Caspian were found in the environment with absolute oxygen concentration over 3.63 ml/l and with relative oxygen concentration over 59%.Wide ecological valency for oxygen is typical for Niphargoides similis (G. O. Sars), Gammarus pauxillus Grimm, Dikerogammarus haemobaphes (Eichwald), Gammarus ischnus Stebbing, and Niphargoides macrurus (Sars).

Critical assessment on operating water droplet sizes for fire sprinkler and water mist systems

With recent developments in the design and manufacturing process of water-based fire suppression systems, more advanced technologies such as water mist systems have expanded in their building application. In this article, the critical fire suppression mechanisms of water mist systems and conventional fire sprinklers are investigated and compared, with emphasis on the influence of water droplet sizes on the fire suppression mechanisms. Applying computational fluid dynamics (CFD), a fully ventilated fire compartment room has been considered where a methane pool fire was placed at the centre. The considered fire suppression systems were placed directly upon the fire. Thermocouple and gas probes were applied in the computational domain to identify different stages of the fire suppression process, as well as to evaluate the suppression performance. The velocity field was analyzed to examine the penetration effect of suppression systems. Relative humidity and oxygen concentration data obtained by gas analyzers were also studied to further understand the droplet/fire interaction behavior. It was found that latent cooling, volumetric displacement, and dilution of oxygen and fuel were the main suppression mechanisms for water mist systems, as smaller droplets evaporate more efficiently compared to larger ones. On the other hand, for sprinklers, heat extraction by water droplets from the fire was found to be the main suppression mechanism, and the evaporation effect is not as significant as in water mist systems. According to in-depth parametric studies of water droplet sizes, recommendations for the optimal running conditions have been provided for both systems.

Luminescence Mechanism in Amorphous Silicon Oxynitride Films: Band Tail Model or N-Si-O Bond Defects Model

Silicon oxynitride films are one kind of important gate dielectric materials for applications in the fabrication of silicon CMOS integrated circuits (ICs), which have been widely and deeply studied. However, with the significant demand of the technologies for Si-based monolithic optoelectronic ICs, the research efforts on the optoelectronic applications of these materials have been continually increasing, particularly in the study of light emission properties and recombination mechanisms. In this paper, we first briefly outline the present photoluminescence (PL) mechanisms in amorphous silicon oxynitride (a-SiOxNy) films. Since the PL properties and recombination processes are affected by both structural disorder and chemical disorder, the PL mechanism has been still unclear and even controversial until now. Among these various PL recombination models, the band tail states and defect states models have gained general consensus. Recently a N-Si-O bond defect model has been reported, which depends on relative atom concentration of oxygen and nitrogen in the silicon oxynitride materials. It has been revealed that oxygen bonding plays a key role not only in reducing the structural disorder, but also in creating N-Si-O (Nx) defect states in the band gap. The characteristics of two models, namely band tail and N-Si-O bond defects, have been discussed in detail. Finally it has been shown that by controlling the chemical composition of these non-stoichiometric silicon oxynitride materials, the optical and electronic properties can be improved.

A novel mixed-potential type NH3 sensor based on Ag nanoparticles decorated AgNbO3 sensing electrode synthesized by demixing method

Solid-electrolyte type sensors based on composite sensing electrodes (SE) have attracted extensive attention due to their excellent sensitivity and anti-interference property. Herein, we prepare AgNbO3/Ag (ANO/Ag) composite SE for the solid-electrolyte type NH3 sensor using a facile demixing method. Compared with pristine ANO-SE, the sensor based on ANO/Ag-SE exhibits larger response signal, higher sensitivity and lower detection limits. What’s more, the anti-interference capability of the sensor toward NOx is effectively enhanced. The effect of the molar ratio of Ag to Nb on the performance of the sensor is also investigated. When the molar ratio of Ag:Nb is 1.05:1, the sensor exhibits largest response signals and sensitivity (−91.2 mV/decade) to NH3. In the meantime, the response signal of the sensor to a fixed NH3 concentration almost keeps constant under different relative humidity (RH) and oxygen concentrations. Thus, the demixing method will provide a new approach for the fabrication of composites SEs with high performance for gas sensors.

463 Hypoxia-inducible factor-1α play a critical role in UVB-induced tumorigenesis by affecting DNA repair capacity and oxidative stress

Hypoxia inducible factor (HIF) 1 is a heterodimeric transcription factor consisting of α and β subunits. The β subunit is constitutively expressed, while the expression of the α subunit is regulated by the relative concentration of oxygen. When stabilized, HIF-1α play a pivotal role in many biological processes by affecting the expression of hundreds of genes involved in angiogenesis, cell growth and apoptosis, cell adhesion and migration, the energy metabolism and DNA repair. Others and we showed that HIF-1α is constitutively expressed in mouse and human epidermis and that HIF-1α plays an important role in the skin, especially in local and systemic adaptation to environmental stresses including ultraviolet (UV) radiation. However, little information is available about its role in photocarcinogenesis. Using a multistage model of UVB radiation-induced skin cancer, we show that the knockout of Hif-1α in the epidermis prevents tumorigenesis, but at the same time triggers the formation of hyperkeratotic plaques. Our results indicate that the absence of oncogenic transformation in Hif-1α-ablated mice is related to increased DNA repair in keratinocytes. Indeed, Hif-1α ablation in the epidermis leads to more proficient removal of UV-induced DNA damage via boosting DNA repair machinery. Consequently, impairing the DNA repair machinery by ablating xeroderma pigmentosum C restores the UVB-induced neoplastic transformation of Hif-1α-ablated keratinocytes. Concerning the formation of hyperkeratotic plaques in irradiated K-Hif-1-/- mice, a causative role of the disturbance of the epidermal redox balance was found. Accordingly, the development of hyperkeratotic plaques is blocked by chronic antioxidant treatment. Altogether, our results show that the deletion of Hif-1α in keratinocytes has two profound effects on the skin’s responses to UVB exposure: it leads to decreased tumorigenesis by promoting DNA repair efficiency; and it causes skin hyperkeratosis by affecting the redox regulation machinery in keratinocytes.